A voltage converter can be used to convert a lower voltage to a higher voltage (step-up operation) or to convert a higher voltage to a lower voltage (step-down operation). In some cases, a switched capacitor DC/DC converter employing a fractional conversion technique may be used. This technique reconfigures power switches based on input voltage (Vin) and output voltage (Vout) to achieve higher power efficiency than linear regulation does. Typical switch configurations for step-up operation include 1:1, 2:3, 1:2 and 1:3, and typical switch configurations for step-down operation include 1:1, 3:2, 2:1 and 3:1.
Some previously developed charge pumps are capable of providing only one direction of voltage conversion—either step-up or step-down. Other previously developed charge pumps are capable of both step-up and step-down operation. However, such other previous designs are efficient only one direction of voltage conversion. That is, a previously developed charge pump which can efficiently convert a lower voltage to a higher voltage cannot efficiently convert a higher voltage to a lower voltage. Likewise, a previously developed charge pump which can efficiently converts a higher voltage to a lower voltage cannot efficiently convert a lower voltage to a higher voltage.